Cabinet making and carpentry in general require precise location of hardware such as hinges, pulls (handles, knobs) and fasteners. The installation of electrical fixtures also requires accurate placement relative to some reference point or at a given spacing between fixtures.
Hole saws are well known and widely used for making circular holes of specific diameters. The holes can be accurately placed by center to center measurement. The hole saw is attached to a drill bit which acts as a pilot to guide the hole saw at the location determined by the center-to-center measurement.
One of the major problems encountered in the use of hole saws occurs when a hole is drilled incorrectly and needs to be redrilled to a larger size. Under current practice, in order to properly center the new hole, the existing hole must be plugged so that the pilot drill bit can be used. This results in extra work and lost time.
It would be desirable to provide a hole saw which would permit correct centering of a new hole without having to plug the existing hole. The present invention provides such a device.